Fluid cylinder and piston assembly

ABSTRACT

A fluid cylinder and piston assembly which comprises an elongated housing defining a fluid chamber to one end of which is secured an attaching member having an eye for securement to a force absorbing member and a piston and piston rod contained in the fluid chamber for reciprocation therein. The piston is welded to one end of the piston rod and the other end of the piston rod extends outwardly of the elongated fluid chamber and is provided with a screw-in attachment eye for securement to force transmitting member. At the rod end of the elongated housing a removable cartridge is provided carrying a rod seal for sealing the cylinder chamber and a retainer member or gland is screwed into the cartridge from the outside of the cylinder for protection and retainment of the rod seal carried by the removable cartridge and which is provided with a wiper seal to continuously wipe the surface of the piston rod. The screwed-in eye connection at the end of the piston rod is provided with a tapered surface engaging a tapered surface within the piston rod end to lock the eye attachment member to the piston rod in such fashion as to remove load stresses from the threaded connection.

United States Patent [72] Inventor William E. Little PrimaryExaminerMartin P. Schwadron West Burlington, Iowa Assistant ExaminerR.H. Lazarus [2l Appl. No. 27,792 Attorney-Cullen, Settle, Sloman & Cantor[22] Filed Apr. 13, 1970 [45] Patented Oct. 12, I971 [73] Assignee J. I.Case Company Racine, w ABSTRACT: A fluid cylinder and piston assemblywhich comprises an elongated housing defining a fluid chamber to one endof which is secured an attaching member having an eye [54] FLUIDCYLINDER AND PISTON ASSEMBLY for securement to a force absorbing memberand a piston and 4Claims,4Drawing Figs. piston rod contained in thefluid chamber for reciprocation l 92 255 therein The Piston is welded toone end of the Piston rod and [52] U s C 151/41 73 the other end of thepiston rod extends outwardly of the elon- [51] In CL Fl6j 1/10 gatedfluid chamber and is provided with a screw-in at- [50] 287/125, tachmenteye for securement to force transmitting member. 92/255 At the rod endof the elongated housing a removable cartridge is provided carrying arod seal for sealing the cylinder [56] Ref Cit d chamber and a retainermember or gland is screwed into the UNITED STATES PATENTS cartridge fromthe outside of the cylinder for protection and 2 405 402 8 1946 C 151 22retainment of the rod seal carried by the removable cartridge 25443043/1951 s g 151 41/73 and which is provided with a wiper seal tocontinuously wipe 268532O 8/1954 en ec 1, the surface of the piston rod.The screwed-in eye connection 3l5807l 1 141964 at the end of the pistonrod is provided with a tapered surface ut engaging a tapered surfacewithin the piston rod end to lock FOREIGN PATENTS the eye attachmentmember to the piston rod in such fashion 500,583 3/1954 Canada l51/41.73as to remove load stresses from the threaded connection.

108 HO I20 I00 H8 TU I r I24 I12 I04 mmmmm 1m 3.611.881

SHEET 1 0F 2 INVENTOR WILLIAM E. LITTLE.

BY- CULLEN, SETTLE, SLOMAN8 CANTOQ ATT'YS.

PATENTEU [lCT 2l97l I 3511.881

sum 2 or 2 I INVENTOR WILLIAM E. LITTLE.

B Y: cuu. EN, SETTLE, SLOMAN a CANTOR.

ATT' Y5.

FLUID CYLINDER AND PISTON ASSEMBLY BACKGROUND OF THE INVENTION Thepresent invention relates to fluid cylinder and piston rod assembliesand more in particular to a fluid cylinder assembly of the expendablelink or linear actuator type having connecting members at both ends forconnection to force-absorbing or force-transmitting members.

Fluid cylinders and piston rod assemblies such as hydraulic linearactuators are widely employed in air craft installations and earthmoving and construction machinery to function as an extendable link orjack to operate various devices. Due to the relative length of theselinear actuators, various problems have been encountered in properlysecuring the piston to the end of the piston rod and maintaining thepiston rod throughout its length in centered axial alignment within thecylinder chamber which requires an accurate bearing support for thepiston rod at the other end of the cylinder opposite from the piston endwhich needs to have a bore accurately centered in concentricrelationship relative to the longitudinal axis of the cylinder chamber.

A further problem has been encountered in maintaining an effective sealbetween the piston rod. and the cylinder chamber which would positivelyprevent any leakage therefrom and at the same time would be accessiblefor replacement or. servicing. This, in the past, was extremelydifficult to accomplish, particularly in view of the requirement ofproviding a concentric rod bearing at the open end of the cylinderchamber to obtain the required rod alignment and piston rod support.

A further, and more serious difficulty, has been encountered in properlysecuring a connecting member to the end of the piston rod extendingoutwardly of the cylinder. This connecting member at the end of thepiston rod is subject to high loading stresses during operation of thelinear actuator and the connection between the piston rod and theconnecting member is subject to extreme wear. Although the connectingmember could be made integral with the piston rod end such as by meansof a forging, this is not desirable, since it would preclude servicingof the seal and piston rod bearing at the open end of the cylinderthrough which the piston rod extends. Thus, the connecting membergenerally is screwed into the piston rod end for selective removal ofthe connecting member from the piston rod if the seal and rod bearingassembly has to be serviced. However, the plain, screwed-in connectionhas been found to be unsatisfactory particularly when subjected toextreme loading as is frequently encountered by the use of such linearactuators in construction or earth moving machinery. Under a heavy loadthe threaded connection of the connecting member and the piston rodwears out quickly and the connecting member has to be replaced, and thethreads in the piston rod have to be reworked frequently to maintain asolid connection.

SUMMARY OF THE INVENTION ln consideration of the above difficulties anddisadvantages of conventional fluid cylinders, such as linear hydraulicactuators, the present invention provides an improved fluid cylinder andpiston rod assembly which obviates most of the aforegoing disadvantages.

The fluid cylinder and piston rod assembly of the present inventioncomprises an elongated cylinder having fluid inlets disposed at oppositeends thereof. One end of the cylinder is closed by a connecting memberprovided with an eye or the like, normally for connection to astationary part or nonmovable member of the machinery or hydraulicsystem in which the fluid cylinder is being used. The elongated cylinderprovides a fluid chamber for reception of a piston and piston rodassembly longitudinally movably disposed therein. The piston ispermanently welded to one end of the piston rod and correctly centeredin coaxial relation relative to the central longitudinal axis of thefluid cylinder. The cylinder is subject to selective fluid pressure ateither end to selectively extend the piston rod from the cylinder orretract the piston rod within the cylinder to thereby lengthen orshorten the effective length of the linear actuator.

The welded-on piston and piston rod construction is preferred to insurelonger piston and cylinder life because of the elimination of separateretainer members to secure the piston to the piston rod.

The other end of the elongated cylinder receives a removablecylindrical, cartridge which has a central bore for the extension of thepiston rod therethrough and which carries the piston rod seal. Removablysecured within the cartridge from the outside thereof is a cylindricalsleeve performing a multiple function, i.e., the sleeve acts (1) as asealing gland for retainment and protection of the rod seal, (2) as acarrier for a wiper seal outwardly of the assembly for continuouslywiping the piston rod and, (3) as a rod bearing concentrically alignedrelative to the central longitudinal axis of the cylinder to maintainthe piston rod, in all phases of operation, in correct centeredalignment. The piston rod bearing is of such axial length so as toprovide sufficient axial support for the piston rod to prevent theintroduction of excessive bending stresses to the piston rod underapplication of loadsmisaligned with the axis of the rod.

A connecting member is removably attached to the outer end of the pistonrod to permit easy access and servicing of the rod seal and bearingassembly by removal of the connecting member from the rod. Theconnecting member is provided with a threaded shank, and the rod endisprovided with a cooperating threaded bore to receive the threaded shank.

The threaded bore in the rod end is provided with an outwardly taperedportion providing a shoulder between the tapered portion and thethreaded portion of the bore. The connecting member is likewise providedwith a tapered por tion for mating engagement with the internal taperedportion in the piston rod bore and a groove is provided on the shank ofthe connecting member between the threaded portion of the shank and thetapered portion,

Upon engaging of the threaded shank portion of the connecting memberwithin the threaded end of the piston rod and screwing the connectingmember inwardly the connecting member becomes seated against theshoulder within the bore of the rod just prior to engagement of thecooperating tapered surfaces on the connecting member and in the bore.Further tightening of the connecting member within the bore at apredetermined torque causes full engagement of the two taperedsurfacesand ultimately causing the material of the shoulder portion inthe rod bore to be deformed radially into the groove of the connectingmember to thereby rigidly lock in the connecting member to the pistonrod end. Removal of the connecting member from the piston rod end isaccomplished by application of a reverse torque in which instance theshoulder formed by the groove adjacent the threaded shank portion of theconnecting member displaces the plastically deformed shoulder materialwithin the bore of the piston rod end outwardly to permit removal of theshank portion from the bore.

The present construction provides various technical advantages overconventional linear actuators having a piston rod and removableconnecting member attached thereto. The tapered engagement of thetapered portion on the connecting member with the internally taperedportion of the bore provides a twofold purpose of great advantage byfirst: causing plastic deformation of material in the bore of the rod toflow into a retaining groove provided on the shank portion of theconnecting member to thereby securely and rigidly locking the connectingmember to the rod and, secondly: providing a load bearing surfacebetween the rod and the connecting member which is not subject to anywear and which additionally removes any load from the threadedconnection which, as explained earlier, has been the primary source ofearly breakdown at the rod end and connecting member.

The removable connecting member also provides for easy servicing of therod seal and bearing assembly, removably retained in the cylinder end.

Further features and advantages of the present invention will becomereadily apparent by reference to the following detailed description tobe read in connection with the appended drawings which illustrate apreferred form of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings FIG. 1 illustrates acylinder and piston rod assembly of the linear actuator type shownpartly in cross section and embodying the features of the presentinvention;

FIG. 2 is an enlarged partial sectional view of the rod end of thecylinder assembly shown in FIG. 1;

FIG. 3 is a separate view of the rod end showing the connecting memberonly partly screwed into the rod end; and

FIG. 4 is a perspective exploded view of the rod end portion of thecylinder assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1 thereis shown a fluid cylinder and piston assembly of the hydraulic linearactuator type generally indicated at It) comprised of an elongatedcylindrical member or tube 12 which is opened at both ends. Attached toone end of the tube 12 is a connecting member 14 which has a cylindricalinner end 16 providing a pilot portion 18 adapted to fit into the end ofthe tube 12. The cylindrical inner end 16 is welded at 20 to the tube 12to provide a fluid tight assembly between the connecting member 14 andthe tube 12.

The connecting member 14 has a fluid inlet 22 which is in communicationwith a pressure chamber 24 within the cylindrical inner end portion I6.Outwardly, the fluid inlet 22 communicates with the bore 26 of an inletfitting 28 attached to the connecting member 14 by means of welding orthe like.

It will be understood that the inlet end of the fitting 28 isconventionally connected to a source of fluid under pressure (not shown)to selectively supply fluid under pressure into the pressure chamber 24.

The connecting member 14, attached to the tube 12, is rearwardlyprovided with an eye 30 adapted for connection to a stationary oractuated member (not shown) provided on the machinery in which thelinear actuator is embodied. The use of linear actuators and theirinstallations in earth moving machinery or the like, to operate thevarious implements or auxiliary attachments of the machine, is widelyknown in the art and need not further be described.

The tubular member 12 forms an elongated cylinder providing an elongatedfluid chamber 32 in which is disposed for reciprocation a piston 34secured to the end of a piston rod 36 which extends in axially centeredrelationship longitudinally through the chamber 32 towards the front endof the tubular member 12.

The piston 34! is attached to the end 38 of the piston rod 36 by meansof splines or serrations 40 and is thereafter ring welded to the pistonrod 36 as at 42 and 44 at both sides of the piston 34. This attachmentof the piston 34 to the piston rod 36 provides a rigid permanentconnection adapted to maintain the piston and the piston rod in correctaxially centered relationship within the chamber 32 of the tubularcylinder portion 112.

Opposite radial recesses 46 and 48 are provided to extendcircumferentially around the external surface of the piston and whicheach receive a sealing member 50 each having a U- shape lip portion 52resiliently contacting the internal surface 33 of the cylinder chamber32 to seal both sides of the piston 34 to prevent fluid from passingfrom one side of the piston to the other under application of fluidpressure into the chamber 24 or 32. Centrally, the piston 34 is providedwith a circumferentially extending wear ring 541 which, if necessary,can be periodically replaced.

The welded-on piston assembly eliminates the need for separate pistonretaining members and assures a rigid attachment of the piston to thepiston rod and maintenance of axial alignment of the piston and pistonrod relative to each other and to the cylinder chamber 32 duringoperation.

The other end of the cylindrical or tubular member 12 extends into oneend of a tubular extension 56 and is welded thereto as at 58. Thetubular extension 56 comprises the rod end of the linear actuator 10 andis provided with a fluid inlet opening 60 communicating with a bore 62provided in a fluid inlet fitting 64. As usual, and as will beunderstood, the inlet fitting 641 which is normally welded to theextension 56 is fluidly connected to a source of fluid under pressure(not shown) for introduction of fluid into a chamber 57 of the extension56. The chamber 57 of the extension 56 is in constant fluidcommunication with the cylinder chamber 32 forwardly of the piston 34.

The front end of the tubular extension 56 is internally threaded as at66 and receives a sleeve-type cartridge 68 which has a reduced diameterinner end portion 70 extending towards the tubular member 12. Thereduced diameter inner end portion 70 permits fluid to pass from theinlet 60 through the chamber 57 and into the cylinder chamber 32. Theouter end of the sleeve-type cartridge 68 is provided with a radialflange 72 adapted for abutment against the outer end of the tubularextension 56. A screw 74 is provided at the interfaces between thecartridge flange 72 and the outer end of the tubular extension 56 toprevent the cartridge 68 from breaking loose.

The cartridge 68 is provided adjacent its outer end with an externalradial scaling member 76 providing a fluidtight seal between theexternal surface of the cartridge and the internal surface of thetubular extension 56. The cartridge 68 is also provided with an axialbore 78 for the passage of the piston rod 36 therethrough. The bore 78towards the outer end of the cartridge 68 terminates in an enlargeddiameter portion 80 a portion of which is being provided with internalthreads 82. Between the piston rod bore 78 and the enlarged diameterportion of the bore 80, a counterbore 84 is provided and adapted toreceive a sealing member 86. The sealing member 86 is provided withU-shaped lip formations 88 adapted to resiliently abut against theinternal surface of the counterbore 84 and the external surface of thepiston rod 36 in sealing contact therewith.

The enlarged diameter bore portion 80 of the cartridge 68 is adapted toremovably receive a gland member or seal retainer 90 provided withexternal threads 92 adapted to mate with the internal threads 82 in thebore portion 80. The inner end 94 of the seal retainer 90 is adapted, inassembly, to abut inwardly against a shoulder 81 formed internally inthe cartridge member 68 between the counterbore 84 and the enlargeddiameter bore portion 80 to thereby completely cover the rod sealingmember 86 for protection against contamination from the outside.

The seal retainer 90 is provided with an axial bore for the passage ofthe piston rod 36 therethrough having an internal diameter closelyfitting the external diameter of the piston rod 36 so that the innersurface 96 of the retainer bore provides a radial bearing surface forthe piston rod 36 in sliding bearing Contact therewith. The axial boreof the seal retainer member 90 is machined such as to be correctlycentered to be concentric with the longitudinal axis of the cylinder 12so as to maintain the relatively long piston rod 36 in axially centeredposition relative to the piston 34 during extension or contractingmovement of the piston rod in and out of the cylinder 12. The radialbearing surface 96 of the seal retainer 90 is of sufiicient axial lengthso as to provide a rigid support for the piston rod 36 to thereby reducebending stresses on the piston rod under load.

The other end of the seal retainer 90 is counterbored as of 98 toreceive an external sealing member 100 adapted for sealing and wipingcontact with the external surface of the piston rod 36 externally of thecylinder assembly. The outer end of the seal retainer 90 is also formedinto a hexagonal flange portion 102 provided for the application of awrench thereto to tightly screw the seal retainer into the cartridge 68until the flange 102 comes into abutment against the outer surface ofthe cartridge 68 and the inner end 94 of the seal retainer is seatedagainst the inner radial and axial shoulder SI provided adjacent thecounterbore 844 of the cartridge.

It will be seen from the foregoing, that the combined cartridge and sealretainer assembly at the operating or rod end of the linear actuatorprovides an effective and easily serviceable sealing means for theoutwardly extending piston rod 36 and simultaneously provides a rigidradial bearing support for the piston rod. The inner piston rod seal 86is fully protected by the seal retainer 90 against the entrance ofcontaminants and the piston rod 36, during operation of the linearactuator, is continuously wiped clean by the external sealing member 100carried by the seal retainer 90.

The outer end 37 of the piston rod 36 which extends outwardly of theseal retainer 90 is provided with an axially aligned bore 104 having anintermediate threaded portion 106 which terminates into an internallytapered portion 108 at the outer end of the rod forming a shoulder 110between them.

The threaded portion 106 of the piston rod bore 104 is adapted toreceive a threaded shank 112 of a connecting member 114. The connectingmember 114 is provided with an eye portion 116 opposite the shankportion 112 adapted for pivotal attachment to a member (not shown) to beactuated by the linear actuator 10.

The eye portion 116 of the connecting member 114 ter' minates towardsthe shank proportion 112 into a radially tapered portion 118 adapted, inassembly, to mate with the internal tapered portion 108 of the pistonrod bore. A radial groove 120 is formed between the threaded shankportion 112 and the tapered portion 118 providing a shoulder 122 at theend of the tapered portion 118 and an opposite shoulder 124 at the endof the threaded shank portion 112.

With particular reference to FIG. 3 which illustrates a sequence in thethreading of the connecting member 114 into the piston rod bore 104, itwill be seen that as the threaded shank portion 112 of the connectingmember advances along the threaded portion 106 inwardly of the pistonrod bore 104 the shoulder 122 of the tapered portion 118 first abutsagainst the shoulder 110 at the inner end of the tapered bore portion108 in the piston rod bore. Upon initial contact between the shoulders110 and 122 there still remains an infinite clearance between thetapered surfaces 108 and 118. By application of a torque wrench,adjusted to the required torque, the connecting member 114 is thenfurther rotated inwardly of the piston rod bore 104 whereby the torqueapplied by the torque wrench overcomes the resistance offered by theinternal shoulder 110 and the portion 111 of the material between theinternal shoulder 110 and the threaded portion 106 of the piston rodbore will be plastically radially deformed into the groove 120 betweenthe threaded shank portion 112 and the tapered portion 118 of theconnecting member '114 to thereby provide a rigid interlock between theconnecting member 114 and the end of the piston rod 36.

As the material 111, adjacent the internal shoulder 110 is beingradially deformed into the groove 120 the tapered surface 118 of theconnecting member is brought into tight wedging contact with theinternal tapered surface 108 in the piston rod bore. The mating taperedsurfaces 108 and 118 are machined such as to have an interference fit insuch manner as to equally distribute the applied torque load to preventthe piston rod end 37 from swelling up towards the outside.

Initially, as mentioned above, the shoulder 122 abuts against theinternal shoulder 110. Thereafter, as more torque is applied, theopposite tapered surfaces 108 and 118 come together starting at theshoulder 122. As the torque loading increases by application of thetorque wrench to the connecting member 114, the contact between themating tapered surfaces likewise increases until the gap is completelyclosed.

Thus, by this arrangement a more effective and rigid connection betweenthe connecting member and the end of the piston rod has been provided.

Which reference to the exploded view illustrated in FIG. 4 of thedrawings, servicing of the rod end of the linear actuator and the sealassembly thereof is relatively easy to accomplish and the sealingmembers 86 and 100 can be easily removed without damage.

In order to disassemble the rod end of the cylinder assembly, a reversetorque is applied to the connecting member 114 to screw the threadedshank portion 112 out of the threaded portion 106 of the piston rod bore104. As the reverse torque is applied to the connecting member, "theshoulder 124 formed by the groove 120 adjacent the inner end of thethreaded shank portion 112 forces the formerly dis placed material 111radially outwardly of the groove 120 to unlock the threaded shankportion 112 and subsequently irons out the formerly displaced material,so that the shank can be threadedly removed from the piston rod bore104.

After the connecting member 114 has been thus removed from the pistonrod end, the seal retainer member is threaded out of the cartridgemember 68 by the application of a wrench to the hexagonal flange portion102, enabling the member 90 sliding off over the piston rod end. Toremove the cartridge 68 from the tubular cylinder member 56, theretaining screw 74 is removed permitting the application of a tool toscrew the cartridge out of the tubular member 56 along the threads 66.Thereafter, the cartridge can be removed by sliding it off the pistonrod end. Thus, the sealing members 76, 86 and are accessible for easyservicing and replacement, if necessary, whereupon the parts arereassembled again'to the rod end ofthe cylinder in a reverse sequence.

It is evident from the foregoing description and the accompanyingillustrations that the present invention provides an improved linearactuator assembly in the form of an elongated hydraulic cylinder closedat one end and reciprocably containing a piston and piston rod assemblyin which the relatively long piston rod extends outwardly at the otherend of the cylinder.

The piston is welded on to the piston rod in order to insure a prolongedpiston and cylinder life due to the elimination of separate fastening orretainer members.

The rod end of the elongated cylinder is provided with an easilyremovable rod-seal carrying cartridge which, in turn, receives aremovable, combination seal retainer and rod-bearing member which alsocarries an external wiper seal. The rod bearing, provided by the sealretainer member, assures a sufficient bearing support for thereciprocating piston rod in such manner as to reduce bending stresses onthe piston rod under load.

A connecting member in the form of an eye, having a threaded shankportion, is removably secured to the outer piston rod end by means of athreaded connection between the internally threaded shank portion, isremovably secured to the outer piston rod end by means of a threadedconnection between the internally threaded piston rod end and thethreaded shank portion. Mating tapered surfaces are provided in thepiston rod end and on the eye shank adjacent the threaded shank portionfor wedging engagement with each other and a radial groove is providedbetween the threaded shank portion and the tapered portion of heconnecting member which is adapted to receive material from the pistonrod end displaced by forcing the tapered surfaces in the piston rod endand on the connecting member into a tight engagement with each other tothereby provide a rigid interlock between the members.

This arrangement completely eliminates any load on the threadedconnection between the connecting member and the piston rod end sincethe entire load is taken up at the mating tapered surfaces thereby alsoreducing load stresses on the piston rod and connecting member.

Thus, by the present improved construction of the rod end of a hydrauliclinear actuator the service life of the complete cylinder assembly isincreased and down time and repairs will be held at a minimum.

The sealing members 50, 86 and 100 are preferrably made of thermoplasticmaterial such as urethane or the like, and will not blow out or extrudeas fast as conventional V-type seals.

Although the present invention has been described and shown withreference to only one particular embodiment it will be understood thatvarious modifications may be made in the structure and design by aperson skilled in the art to which the invention pertains withoutdeparting from the spirit and essential characteristic thereof and suchmodifications are contemplated to be included within the scope of theappended claims.

I. In a cylinder and piston structure having a piston and piston rodassembly, a piston attached to said piston rod at one end of said pistonrod, the other end of said piston rod having an axial bore comprising afirst portion at the inner end of said bore and being threaded, a secondportion extending to the outer end of said bore and of generally largerdiameter than said first portion, said second portion hang an innercircumferentially tapered surface, a shoulder formed between said firstand said second portion of said bore, a connecting member comprising: ashank portion integral therewith, said shank portion having a threadedend for engagement with the threads of said threaded bore portion, acircumferential groove provided adjacent said groove and said connectingmember for wedging engagement with said tapered surface of said secondportion of said bore when said threaded end of said shank portion isthreaded completely into said threaded portion of said bore.

2. In the structure as defined in claim I, said groove providing aninner shoulder adjacent said threaded shank portion and an oppositeouter shoulder adjacent said threaded portion, said outer shoulder beingadapted to contact said shoulder formed between said first and secondportion of said bore prior to contact of said tapered portion with saidtapered surface of said bore.

3. In the structure as defined in claim 2, said groove being adapted toreceive material displaced from the inner surface of said rod end uponwedging engagement of said tapered portion with said tapered surface ontorque application of a predetermined magnitude to said connectingmember to thereby lock said connecting member to said rod end.

4. In the structure as defined in claim 3, said inner shoulder beingadapted to displace said displaced material radially outwardly of saidgroove upon application of a reverse torque to said connecting member.

1. In a cylinder and piston structure having a piston and piston rodassembly, a piston attached to said piston rod at one end of said pistonrod, the other end of said piston rod having an axial bore comprising afirst portion at the inner end of said bore and being threaded, a secondportion extending to the outer end of said bore and of generally largerdiameter than said first portion, said second portion hang an innercircumferentially tapered surface, a shoulder formed between said firstand said second portion of said bore, a connecting member comprising: ashank portion integral therewith, said shank portion having a threadedend for engagement with the threads of said threaded bore portion, acircumferential groove provided adjacent said groove and said connectingmember for wedging engagement with said tapered surface of said secondportion of said bore when said threaded end of said shank portion isthreaded completely into said threaded portion of said bore.
 2. In thestructure as defined in claim 1, said groove providing an inner shoulderadjacent said threaded shank portion and an opposite outer shoulderadJacent said threaded portion, said outer shoulder being adapted tocontact said shoulder formed between said first and second portion ofsaid bore prior to contact of said tapered portion with said taperedsurface of said bore.
 3. In the structure as defined in claim 2, saidgroove being adapted to receive material displaced from the innersurface of said rod end upon wedging engagement of said tapered portionwith said tapered surface on torque application of a predeterminedmagnitude to said connecting member to thereby lock said connectingmember to said rod end.
 4. In the structure as defined in claim 3, saidinner shoulder being adapted to displace said displaced materialradially outwardly of said groove upon application of a reverse torqueto said connecting member.